Fabrication And Sers Properties Of Large-Scale Vertical Arrays Of Gold Nanorods

In recent years,plasmonic materials have attracted much attention due to their unique photoelectric characteristic and potential applications in sensing,imaging and catalysis.However,plasmonic device properties are seriously affected by both nanoparticle morphology and stack architecture.Therefore,it is important to fabricate ordered nanoparticle arrays with optimized structures.Gold nanorod is considered as one of the most influential plasmonic materials,due to its chemically stable,adjustable light response in range of visible and near infrared region as well as easy preparation.Vertical arrays of gold nanorods as SERS substrates for trace detection,early diagnosis have made remarkable achievements.However,the existing method of preparation gold nanorod arrays suffered from some unfavorable factors,such as mixed structure,poor ordering,small assembly area,which hinder its practical application.In particular,the stability and reliability of SERS signal is poor.Therefore,building large-scale ordered gold nanorod vertical arrays is of great value in both application and basic research.At present,solvent evaporation is the simplest and the most popular method.The gold nanorods will form self-assembly arrays when volume fraction is increased by solvent evaporation.This method slightly depends on apparatusand but seriously relies on the environment.It is deserved to optimizing assembly process by adjusting evaporation environment to enhance the degree of the order and scale,in order to further improve stability and reliability of its SERS performance.Our work mainly focuses on the following two aspects:1.Vertical arrays of gold nanorods are fabricated through controllable the slow solvent evaporation method:The evaporation rate is a key factor of formation of ordered arrays,which is jointly determined by the temperature and humidity.The wettability of the substrate affects the area of the self-assemble.Therefore,a suitable system environment is a prerequisite for fabricating large-scale ordered arrays.Through regulating the temperature,humidity and varying different substrates,we can fabricate highly ordered gold nanorod vertical arrays with different morphology and size.Especially,the vertical array with1mm width and bilayer of gold nanorod is prepared using the nanorod which aspect ratio is 2.XRD data indicates the gold nanorod arrays tend to be vertically aligned and the degree of order is more than 95%.Multiple substrates are employed to fabricate the arrays,in which large-scale standing array is fabricated when using corundum substrate.2.Test the stability and reliability of the SERS signal.We choose MG as the probe molecule,using the gold nanorod vertical arrays as the active substrate for SERS detection,the detection limit can reach up to10^-15 M.The homogeneity and stability of the substrate is tested by Raman mapping.The RSD is 12.6%in the area of 26×29?m² which randomly selected and is 17.1%in another area of 0.7×0.7 mm²,which mainfest the good homogeneity.The RSD calculated from 5 different gold nanorod vertical arrays with the same structure is 8.9%,which indicates good array-to-array stability.The substrate is easily recovered just by cleaning with plasma and exhibit excellent repeatability in different sample cross test.